1. Field of the Invention
The present invention relates generally to human-computer interaction, and more particularly, to haptic computer interfaces which measure position/orientation input from a computer user's hand while providing force/torque output to the user's hand.
2. Description of Prior Art
The term “haptics” refers to the human sense of touch. In recent decades, there has been a great deal of attention to providing computer interfaces that, in addition to the usual keyboard and mouse input devices, and visual output provided by the display on a monitor, can also engage the computer user's sense of touch. Generally, these haptic devices have a manipulandum or handle that can be grasped and moved about by the user to provide position input to a computer, in a manner similar to that of a computer mouse. Unlike a mouse, which can be moved in the plane of the desktop [2 degrees of freedom (DOF)], some haptic devices allow translational movement in all 3 DOFs while providing force back to the user's hand, and still others add rotational DOFs which also provide torque feedback. Of particular interest are those haptic devices with 6 DOFs, because 6 DOFs are needed to position and orient a rigid body in space.
Prior art haptic devices fall into two broad categories: i) electromechanical devices which are small robot arms with serial or parallel kinematic configurations (or a combination of serial and parallel aspects), and ii) non-mechanical devices which use principles of magnetic levitation. Haptic devices in the first category have been available commercially for some time from companies such as Sensable Technologies, Woburn, Mass., USA; Immersion, San Jose, Calif., USA; Mimic Technologies Inc., Seattle, Wash., USA; Force Dimension, Nyon, Switzerland; MPB Technologies Inc., Montreal, Quebec, Canada; Quanser, Inc., Markham, Ontario, Canada; Moog-FCS, Nieuw-Vennep, Netherlands; and Haption S. A., Soulge sur Ouette, France. Devices marketed by these and other firms, being electromechanical in nature, necessarily incorporate motors, encoders, links, joints, and transmission elements such as gears, capstans, cables, or belts. Whereas this body of prior art may serve as background for haptic interface devices per se, the present invention achieves similar functional goals through a fundamentally different mechanism, namely, magnetic levitation. Haptics based on magnetic levitation is capable of much higher performance since it can avoid unwanted artifacts associated with electro-mechanical devices.
Magnetic levitation (or magnetic suspension) devices have a long history and depend on various principles for their operation. These include magnetic bearings and magnetic levitation (“maglev”) trains, as well as numerous toys illustrating magnetic levitation. Of particular interest is Downer, et al., U.S. Pat. No. 4,700,094, issued Oct. 13, 1987, which describes a magnetic bearing utilizing Lorentz forces for maintaining the rotation of a flywheel which may be subject to small disturbances. Of tangential interest is Anderson, et al., U.S. Pat. No. 4,156,548, issued May 29, 1979, which describes a magnetic suspension and pointing system utilizing Maxwell forces. Of closest interest is Hollis, U.S. Pat. No. 4,874,998, issued Oct. 17, 1989, which describes a magnetically levitated fine motion robot wrist using Lorentz force actuation with a workspace of several millimeters. None of this art pertains to haptics or haptic devices.
The first use of magnetic levitation principles for a haptic device is disclosed in Hollis and Salcudean, U.S. Pat. No. 5,146,566, issued Sep. 8, 1992. This patent shows a hexagonal levitated body supported by Lorentz forces and using optical position sensors, rendering it capable of six-degree-of-freedom (DOF) motion and force/torque output. It is described as an input/output system for computer user interface, i.e., it describes a haptic device. Further, the invention describes, in general terms, various software elements for connecting and communicating between a computer user's software program and the magnetic levitation device. The device lacks the large workspace, light weight composite levitating element, interchangeable handles, reorientation capability, and automatic software procedures of the present invention.
The paper “Lorentz levitation technology: a new approach to fine motion robotics, teleoperation, haptic interfaces, and vibration isolation,” by R. L. Hollis and S. E. Salcudean, appeared in the International Symposium for Robotics Research, Hidden Valley, Pa., in Oct. 1-3, 1993, and further describes haptic interaction and other applications using magnetic levitation.
A motion scaling tele-operating system with force feedback suitable for microsurgery is disclosed in Salcudean, et al., U.S. Pat. No. 5,382,885, issued Jan. 17, 1995. The system uses a pair of hexagonal magnetic levitation devices in a master/slave arrangement providing haptic feedback to the user. An alternative magnetic levitation tele-operation system with haptic feedback is described in the paper “Design and control of a force-reflecting teleoperation system with magnetically levitated master and wrist,” Salcudean, Wong, and Hollis, IEEE Transactions on Robotics and Automation, Vol. 11, pages 844-858, December, 1995. The paper “Interacting with virtual environments using a magnetic levitation haptic interface,” by P. Berkelman, R. Hollis, and S. Salcudean, in IEEE International Conference on Robotics and Automation, Pittsburgh, August, 1995, pages 2296-2301, further describes haptic interaction between a computer program and a magnetic levitation device. Again, these devices lack the large workspace, light weight composite levitating element, interchangeable handles, reorientation capability, and automatic software procedures of the present invention.
Salcudean, et al., disclose an active joystick with optical position sensing in U.S. Pat. No. 6,195,083 B1, issued Feb. 27, 2001, which has a cubic configuration and very small workspace. This device was planned for commercialization, but never materialized. This device lacked the large workspace, light weight composite levitating element, interchangeable handles, reorientation capability, and automatic software procedures of the present invention. U.S. Pat. No. 5,790,108 issued to Salcudean, et al., on Aug. 4, 1998 describes a specific application of the Lorentz force coils in a hand controller.
The paper “Design of a hemispherical magnetic levitation haptic interface device,” by P. Berkelman, Z. J. Butler, and R. L. Hollis, in the ASME International Mechanical Engineering Congress and Exposition, Atlanta, November 1996, DSC-Vol. 58, pages 483-488, describes a design for a large workspace Lorentz magnetic levitation haptic device. This device lacks the light weight composite levitating element, interchangeable handles, reorientation capability, and automatic software procedures of the present invention.
Watanabe, et al. describe a magnetic actuator with reduced magnetic flux leakage and haptic sense in U.S. Patent Application Publication No. US 2004/0059245 A1, published Mar. 25, 2004 and in U.S. Pat. No. 7,336,006 B2. A similar much earlier design, by R. Hollis, “Ultrafast electrodynamic X, Y, and theta positioning stage,” was disclosed in U.S. Pat. No. 5,153,494, issued Oct. 6, 1992. These devices do not use magnetic levitation.
Li, et al., in U.S. Pat. No. 6,483,499 B1, issued Nov. 19, 2002, disclose a 3D sculpturing input device using a magnetized stylus held by the user. Hu, in U.S. Patent Application Publication No. US 2006/0209019 A1, published Sep. 21, 2006, discloses a magnetic haptic feedback system and methods for virtual reality environments. The system uses a magnetized tool upon which forces are generated with electromagnets. Neither of these devices use magnetic levitation as in the present invention.
The paper “A novel coil configuration to extend the motion range of Lorentz force magnetic levitation devices for haptic interaction,” by P. Berkelman, Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems, San Diego, Oct. 29 through Nov. 2, 2007, pages 2107-2112, describes a magnetic levitation haptic device with permanent magnetic circuits and coil design to permit large translational and rotational motion. This device, while having a larger motion range than the present invention, does not have a light weight composite structure, and lacks a viable scheme for providing high resolution position/orientation sensing.
In summary, each of the prior art haptic devices and systems, whether based on electro-mechanical methods or on magnetic levitation methods suffers from one or more limitations which the present invention overcomes.